1. Field of the Invention
The invention relates to an ink jet printer for printing data on a recording medium by ejecting ink from ink jet heads, and more particularly to an ink jet head connection unit for connecting ink supply paths for supplying ink to the ink jet heads.
2. Description of the Related Art
A conventional method of connecting an ink jet head to an ink supply path has been to use an adhesive to join the substrate constituting the ink jet head and the component constituting the supply path, thereby forming an ink supply path and supplying ink to the ink jet head.
For example, U. S. Pat. No. 4,500,895 discloses an example of forming an ink supply path that supplies ink to an ejection mechanism (mechanism for providing ejection force to ink) by using an adhesive to join a glass or ceramic substrate possessing an jet feed hole to a recess of a plastic backing plate possessing a groove and a feed hole.
Multiple thin-film thermal jetting resistors are formed on the surface of this substrate, and the jet feed hole to a thermal jetting resistor area is formed through the substrate. A groove is provided in the recess of the backing plate, in the position corresponding to the jet feed hole of the substrate. Furthermore, the feed hole is also provided in the backing plate to connect the groove to a flexible ink reservoir. A capillary supply path for supplying ink from the ink reservoir to the ink jet resistor area is formed by joining the substrate with the back plate.
However, this conventional method had the problems described below.
It is difficult to evenly apply an appropriate thin coat of adhesive to the substrate and the backing plate used for forming ink jet heads. Especially, if the amount of adhesive is excessive, the adhesive flows into the ink supply path, clogging the capillary supply path and preventing ink supply to the ejection mechanism, and as a result, thus preventing ink droplet ejection. On the other hand, if the amount of adhesive is in sufficient, a gap is created in the junction surface, leaving the potential of ink leakage from the gap.
Furthermore, because the surface on which the adhesive has been applied is exposed during the assembly of the ink jet, foreign materials such as dust may adhere to the adhesion surface, leaving the risk of creating gaps in the junction surface as described above. Moreover, since the substrate on which an ejection mechanism has been formed is adhered to the surface to which the adhesive has been applied, it is difficult to precisely position the substrate against the backing plate for adhesion.